digital image processing hongtao lu dept. of computer science sept. 2006
TRANSCRIPT
Digital Image Processing
Hongtao Lu
Dept. of Computer Science
Sept. 2006
Text Book
DIGITAL IMAGE PROCESSING
Kenneth R. Castleman
清华大学出版社 / Prentice Hall
1997
Reference Books
Digital Image Processing (Second Edition)
Rafael C. Gonzalez and Richard E. Woods
电子工业出版社 原版影印 2002 年 数字图像处理学,阮秋琦 编著,电子工
业出版社, 2001 年
Chapter 1 Images and Digital Processing1.1 Introduction
What is an image?
An image may be defined as a two-dimensional function, f(x,y), where x and y are spatial (plane) coordinates, and the amplitude of f at any pair of Coordinate (x,y) is called the intensity or gray level of the image at that point.
What is a digital image?– When x, y and the amplitude f(x,y) of an image
are all finite, discrete quantities, an image is called a digital image.
– A digital image is composed of a finite number of elements, each such element is called a picture element or a pixel.
– A digital image is a numerical representation of an object
What is Digital Image Processing?– Processing image by means of a digital
computer– Digital image processing is a process that
subjecting a numerical representation of an object to a series of operations in order to obtain a desired result.
1.2 The elements of digital image processing Digitization
– Process of converting a physical image to a digital image
– Spatial sampling (Rectangular sampling)
Physical
Image
– Quantization: representing the continuous intensity value with finite number of integers.
A typical image-processing system
Image Digitizer
Input Image Storage
ComputerOutput Image Storage
Console
Image Recorder
Program Library
1.2.1 The Terminology of DIP
Physical images– Distributions of matter or energy (may be visibl
e or nonvisible)– Multi-spectral images----those having more tha
n one local properties at each location. Color image
Abstract images– Continuous or discrete functions
Types of imagesObjects
Images
Visible images
Pictures
Photographs
Drawings
Paintings
Optical images
Mathematical functions
Continuous
Discrete
Non-visible physical images
Computer Graphics– Processing and display of images of things that
exist conceptually or as mathematical descriptions.
– Generation of a image, given a model that describes the object, its illumination, and the geometry of an imaginary camera.
Computer vision– Developing systems that can interpret the conte
nt of natural scenes.
Chapter 2 Digitizing Images
2.1 Introduction– The Elements of a digitizer
• Sampling aperture
• Mechanism for scanning the image
• Light sensor
• Quantizer
• Output storage medium
2.2 Characteristics of an image digitizer– Pixel size– Image size– Local property measured– Linearity– Noise
2.3 Types of image digitizer– Scan-in and Scan-out Digitizing
2.4 Image-Digitizing Components– 2.4.1 Light Sources
• Incandescent Bulbs
• Lasers
• Phosphors
• LEDs
2.4.2 Light Sensors– Photoemissive Devices ( 光电发射器件 )– Silicon Sensors– Photodiodes( 光敏二极管 )– Phototransistor( 光敏三极管 )
2.4.3 Scanning Mechanisms– Mechanical scanning devices– Electron beam scanning
– Electrostatic deflection ( 静电偏转 )– Magnetic Deflection ( 磁偏转 )– Beam focus ( 电子束聚焦 )
Chapter 3 Digital Image Display
3.1 Introduction– 3.1.1 Image quality
3.2 Display Characteristics– Displayed image size– Photometric resolution ( 光度分辨率)– Gray-scale linearity– Display calibration– Low frequency response
• Pixel polarity
• Pixel interaction
• The Gaussian display spot
• Display spot interaction
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Examples of Fields that use DIP (supplement) Images categorized by electromagnetic (E
M) energy spectrum
510 410 310 210 110 010 110 210 310 410 510 610 710
Energy of one photon
Gamma rays
X-rays Ultra-violet
Visible Infrared Microwaves Radio waves
Gamma-Ray Imaging– Nuclear medicine– Astronomical observations
Positron emission tomography PET A PET image
X-ray Imaging
– X-ray medical diagnostics– Angiography (contrast-enhancement radiograp
hy)– Computerized axial tomography– Astronomy– Applications (e.g. X-ray inspection)
X-ray imaging
An angiogram image Head CT
X-ray imaging
An X-ray image of circuit board
Imaging in the Ultraviolet band
– Fluorescence microscopy– Lithography– Industrial inspection– Astronomical observations
A Fluorescence microscope
Imaging in the visible and infrared bands
– Light microscope
Taxol Cholesterol Surface of audio CD
Remote sensing (multispectral imaging)
Weather observation and prediction
– Automated visual inspection in manufacture industrial
– Pattern recognition
Imaging in the microwave band
Radar
Radar image of Southeast Tibet
Imaging in the Radio band– Medicine (MRI: Magnetic resonance imaging)– Astronomy
MRI Knee
Examples of other imaging modalities Imaging using “Sound”
– Geological exploration (Using sound in the low end of the sound spectrum (hundreds of Hertz)
– Medicine (ultrasound imaging, 1-5 MHz)
Electron microscope
Synthetic image (generated by computer)
– Fractal– 3-D modeling
Fundamental steps in DIP
Color image processing
Wavelets and multiresolution
Compression Morphological processing
Image restoration
Image enhancement
Image acquisition
Segmentation
Representation & description
Object recognition
Problem domain
Ou
tpu
t image attrib
utes
Output images
Knowledge base
Components of an image processing system
Image displays
Computer Mass storage
HardcopySpecialized image processing hardware
Image processing software
Image sensors
Problem domain
Network
Elements of visual perception
Perceived brightness is not a simple function of intensity
An example of simultaneous contrast
Some well-known optical illusion